Video monitoring systems have been widely used in various fields, such as, roads, parking lots, banks, marketplaces, etc. They obtain three-dimensional space information from a two-dimensional image shot by a video camera, such as a speed of a moving object, a length of a vehicle, a height of a person, etc. In order to obtain three-dimensional coordinates corresponding to pixels in the two-dimensional image to thereby infer information in the real world from the shot two-dimensional image, the video camera needs to be calibrated, that is, determining a gesture of the video camera relative to the ground (a rotation angle, a height, etc. of the video camera). As compared with the manual calibration, a video camera calibration is the trend of developing of the video camera calibration in view of workload of personnel and a measuring difficulty.
Generally, the video camera calibration is performed according to a three-dimensional disappearing direction of the three-dimensional world in the video camera coordinate system. In the existing technology, the disappearing direction is estimated mainly based on line segments obtained by edge detection in the video image.